The Contrasting Behavior of Strongly and Weakly Interfacially Active Asphaltenes on the Rheology of Model Waxy Oils

Asphaltenes and waxes are two components of crude oil that cause flow assurance issues. Although the components coexist, few studies have considered the effect of asphaltenes on wax crystallization and gel-forming properties. Furthermore, the current understanding remains contradictory with both wax-alleviating and wax-aggravating behaviors observed. In this study, asphaltenes extracted from a heavy crude oil were fractionated into strongly and weakly interfacially active asphaltenes by partitioning at a water–oil interface. The two asphaltene fractions exhibited contrasting physicochemical properties, with the strongly interfacially active asphaltenes (IAA) being more polar due to their higher heteroatom content (particularly S and O) and forming larger aggregates in the solution compared to the weakly interfacially active asphaltenes (referred to as remaining asphaltenes, RA). The two asphaltene fractions lowered both the wax gelation temperature and wax appearance temperature; however, the effect was comparable. The unit cell lattice structure of the wax particle remained unchanged in the presence of asphaltenes, but the wax particles were found to be smaller with RA compared to IAA. However, the key finding of the study is how the two asphaltene fractions affected the yield strength of the gelled wax. For RA, the yield strength was lowered with an increasing asphaltene concentration, whereas for IAA, the overall effect was to increase the gel yield strength. Because the properties of the wax particles were largely unchanged by the two asphaltene fractions, the result suggests that the asphaltene–asphaltene interaction contributes to the overall yield strength. It was shown that the interaction between RA and RA is repulsive with negligible adhesion, whereas that between IAA and IAA is attractive with strong adhesion. These structure-breaker and structure-maker properties of the two asphaltenes confirm that the asphaltene–asphaltene interaction significantly contributes to modifying the yield strength of a waxy gel

Electron-electron interactions and two-dimensional - two-dimensional tunneling

We derive and evaluate expressions for the dc tunneling conductance between interacting two-dimensional electron systems at non-zero temperature. The possibility of using the dependence of the tunneling conductance on voltage and temperature to determine the temperature-dependent electron-electron scattering rate at the Fermi energy is discussed. The finite electronic lifetime produced by electron-electron interactions is calculated as a function of temperature for quasiparticles near the Fermi circle. Vertex corrections to the random phase approximation substantially increase the electronic scattering rate. Our results are in an excellent quantitative agreement with experiment.Comment: Revtex style, 21 pages and 8 postscript figures in a separate file; Phys. Rev. B (in press

Rochechouart 2017-Drilling Campaign: First Results

No abstract available

Nurture, nature and some very dubious social skills: An interpretative phenomenological analysis of talent identification practices in elite English youth soccer

This paper reports qualitative findings regarding the concepts and practices utilised in talent identification (TI) among professional coaches working in English youth soccer. Using interpretative phenomenological analysis, detailed interviews with seven such coaches are explored, with a view to elucidating the links between understanding, practice, experience and professional context. Findings reveal three superordinate themes, relating to (1) a primarily ‘nurtured’ and trainable understanding of the broad concept of talent itself, (2) an ostensibly contradictory model of semi-static player psychology, and (3) a highly selective mechanism for separating evidence for ‘mental strength’ and ‘social skills’. It is contended that these findings underscore a case for more thorough interrogation of the real worlds inhabited by coaches, such that ideas about ‘good practice’ in TI might be more effectively reconciled with grounded knowledge of the practical everyday necessities of being a coach

New insights into the genetic etiology of Alzheimer's disease and related dementias

Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries